TIG questions


Old 09-28-04, 01:18 PM
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TIG questions

I thought I posted this last night but I guess it didn't go through...
I've seen references to folks using DC inverter stick welders with a TIG torch and argon tank. I understand that it is "scratch start" and doesn't have much heat control. I'm just kind of interested in this because I have an old MIG with a crapped out wire feed that I thought I could convert. I'm interested in doing sheet metal and aluminum. Any input or should I just stick to my good MIG welder and save the $$ I would spend experimenting?
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Old 09-29-04, 02:34 PM
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It's not worth the trouble because the power supply for a MIG welder is fundamentally different than the power supply for a TIG or stick welder. The TIG (and also a stick welder) is a constant current source which means you dail in 80 amps, for example, and it tries to maintain 80 amps by varying the voltage.

A MIG welder, on the other hand, is a constant voltage source and will try to maintain the set voltage (usually shown as just a number on a dial) by varying the current. This will not work with TIG, it will eat up your tungstens (I know, I tried this two years ago before I discovered this info).
Old 09-29-04, 04:09 PM
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Thanks. How about rigging up a torch to one of those DC inverter stick welders?
Old 10-23-04, 10:40 PM
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You'll need AC current to weld aluminum for one. Not saying it can't be done but you'd be better of just buying a uses tig like a miller econo tig. That will get you a good start. Welding aluminum is extremely hard. It will take a year or more of constant practice to get good results that you'll want to show off. Do lots of reading on the subject before you get started and you'll save lots of money on consumables in the long run.
Old 11-06-04, 10:54 AM
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Not all MIG welders are made the same.

I'm repairing a MIG welder. and I have two others. The low end ones.
I also have an AC/DC 230amp stick welder
the main parts are the same in my MIG, as to the stick welder.
My MIG welders have no components inside to regulate a constant voltage.

However, Wire feed is constant. when the wire is feeding into the work it melts into the weld at the same distance.
This keeps the arc length consistent, which in turn keeps the Voltage and Current constant.
Some MIG welders, are in general, stick welders with wire feed units added.

People have been adding wire feed units to stick welders for some time.

I don't see why you cant convert, Some MIG welders to a low end TIG (scratch start).
If the MIG welder has a low output voltage you will not get good penetration for TIG and if the O.C.V. is low it may not scratch start.

What you can do for a TEST.(before you buy a TIG gun)
Drill a hole in one of your replaceable MIG tips to fit a Tungsten electrode.
use eye protection when trying to press fit the electrode into the tip. tungsten may shatter.
when the tip heats up the Tungsten may or may-not fall out?
Do the test on steel.

If the tungsten burns off to fast, you may need to reverse the polarity of your gun.
The Gas, cups, and distance the tungsten extends from the gun is critical the get this to work.
You need to keep the tip shielded with gas at all times.

You must NOT Exceed the duty time of your machine the components inside are under rated and will eventually Fail from expansion and contraction do to increased heating.
TIG is slower and you may go over the duty time frequently.
Old 11-06-04, 03:02 PM
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Voltage-sensing wire feeders


The constant-speed wire feeders can ONLY be used with a CV power source.
The voltage-sensing feeders can be used with EITHER a CC power source (such as a stick machine) OR a CV power source (such as as a MIG machine).

The Miller 3045 FC is a moderately-priced feeder in this category.
Old 11-10-04, 12:22 AM
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constant speed wire feeder

The Statement I found, from your link states.
" A constant speed wire feeder, such as Miller's SuitCase 8RC and 12RC, is used only with a constant voltage (CV) power source."

It did not state ALL, constant speed wire feeders are used only with a constant voltage (CV) power source.

I did not find an explanation why a constant speed wire feeder, will not work on a Low end (CC) welder.
I'm not talking about welds that must be certified.There low end welders.

every now and then, I pickup a low end Mig welder because I know I can repair them to the component level.
The one I'm repairing now has spot weld and stitch weld functions.one of the better ones.
I spent one week drawing a schematic and a second week to identifying a bad integrated circuit that was on the wire feed circuit board. the manufacture removed the part number so most people would need to replace the whole board

The wire feed circuit has NO feed back from the output of the welder (no voltage sensing).
The wire feed unit has a separate 24 volt transformer to power it.
(some welders use the voltage from the welding transformer to power the feed unit)
with that separate transformer the wire feed unit is completely isolated from the HI current welding components
wire feed on this MIG is a constant feed on a CC transformer setup.

The link below is someone that opened up a low end welder made a schematic and built a MIG welder.
his schematic is similar to the one I made.
His wire feed unit is also isolated from the welding transformer. making this a constant speed wire feed unit on a CC setup.

He also makes a note about setting it up for TIG welding. And I agree it can be converted for TIG use.

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